An electronic access control device, such as an electronic combination lock or an electronic alarm system, allows the user to activate or deactivate the access control without the use of the conventional key and mechanical lock mechanism. With the development of microprocessor integrated circuits, it is becoming common to implement microprocessor-based control circuitry in electronic access control devices. Electronic access control devices are known, for example, from U.S. Pat. No. 5,021,776. In this device, and other common electronic access control devices, a microprocessor is used in combination with a keypad and an electrically programmable read only memory (EPROM). The microprocessor compares the combination entered in the keypad by the operator with the combination stored in the EPROM. If the two combinations match, the microprocessor opens the lock.
There are problems associated with previous electronic access control devices. One area of problems concerns the manufacture of the devices, including the difficulty in programming the non-volatile memory, such as the EPROM, for storing the access code and other useful information for the operation of the device. EPROMs, which usually require parallel programming, interrupt the manufacturing process in that they restrict when the manufacturer can program the device. A manufacturer would prefer to program the access code into the EPROM as the last step in the manufacturing process. However, with parallel EPROMs, burning in the code after the device has manufactured is difficult. After the device is soldered together, the manufacturer must contend with integrated circuit pin clips and must worry about interference with other circuitry on the manufactured device. Further, manufacturing, with known electronic access control devices, requires many pin connections which increase manufacturing cost.
Related to the problems associated with the pin connections of the microprocessor integrated circuit (IC) is the concern of device reliability and ease of use. When the device contains a significant number of pin connections, the reliability of the device decreases. Further, serial access to the EPROM to determine the electronic access code is easier than parallel access in terms of pin connections. When the user forgets or loses the access code in the EPROM, a locksmith could plug into the device and retrieve the access code serially without breaking into the safe. However, with parallel EPROMs, serial access is not available.
One common problem associated with previous electronic locks is their potential vulnerability to tampering. A conventional electronic lock receives an access code via an input device such as a keypad or electronic key reader, verifies the access code, and then energizes a solenoid, relay, motor, or the like to open the lock. This arrangement is vulnerable to tampering because if the control circuit is somehow broken in or removed, one can open the lock by “hot-wiring” the control lines for activating the lock-opening mechanism.
Another technically challenging problem is related to the need to provide electrical energy to power the operation of the electronic access control device. For many applications, it is desirable to use a portable or alternative energy source, such as a battery, to power the access control device. A battery, however, has a rather limited amount of electrical energy stored therein. Thus, in many applications it is important to reduce the power consumption of the control circuit and peripheral devices of the access control device to extend the service life of the batteries.
For instance, it is typical to use a solenoid-operated lock in an electronic lock. The consumed by the solenoid in opening the lock is quite significant. Thus, the battery can be rapidly drained by the repeated operation of the solenoid. As another example, it is common to include a low-battery detection circuit in an electronic lock to provide a warning signal to the user when the battery voltage falls below a predetermined level. The operation of the low-battery detection circuit, however, also consumes electrical energy and contributes to the draining of the battery.
Some electronic locks are provided with electronic keys. When an electronic key is presented to a key reader of an associated electronic lock, it transmits an access code to the electronic lock. By using an electronic key, the user does not have to enter manually the access code by means of a keypad. In certain applications, a remote control unit is used which has a radio transmitter to send the access code to the lock without direct electrical contact with the electronic lock.
Although electronic keys are a convenient feature, they have their associated problems. One problem is related to the unauthorized use of the keys. For example, many hotels provide safes equipped with electronic locks in their hotel rooms. Such safes typically allow the hotel guests to set their own access codes. In cases where the hotel guests forget the access codes they set, the hotel management has to send someone with a master key which has a master access code stored therein to open the safes. There is a danger that such a master key may be used for unauthorized opening of other safes in the hotel.
Another problem associated with the use of an electronic key or a wireless access code transmitter is that the key or the transmitter may be lost easily, or the user may simply forget to bring the key or transmitter. This problem is especially serious if the electronic access control device does not provide other means, such as a keypad, for entering the access code.
Vending machines are widely used in various locations as automated means for selling items such as soft drinks, snacks, etc. Traditional vending machines are equipped with mechanical locks, which can be unlocked with a corresponding mechanical key to open the door of the machine to allow reloading of goods and collection of money.
One significant problem with conventional vending machines is the difficulties in managing the distribution and usage of the keys to ensure the security of the locks on the vending machines. The process of collecting money from the vending machines scattered at different places is a very manpower-intensive operation that requires many employees to go into the field with numerous mechanical keys for operating the locks on the vending machines. It requires a considerable amount of attention and efforts to manage and track the distribution of the keys to the field workers to keep the keys secure.
Moreover, the mechanical keys and lock cores of vending machines are a point of attack for vandals. The keys can be lost or copied easily, and the stolen or copied keys may then be used by an unauthorized person to access the machines, and it is difficult to discover such misuses and security breaches. Also, a skilled vandal can easily pick or drill-out the lock core tumblers and measure the key cuts of the lock core tumblers to re-produce a like key and compromise the security. In the event a security breach is identified, the mechanical lock cores of the affected vending machines typically have to be manually replaced, which is a time-consuming and very costly process. Furthermore, mechanical keys and locks are devices that cannot be partially limited in operation they operate indefinitely if in use. Also, they do not have the ability to record access operation attempts of their operation.